#include<stdio.h>
int main()
{
	int i = 0, flat = 1;
	double sum = 0.0;
	for (i = 1; i <= 100; i++)
	{
		sum = sum + flat * (1.0 / i);
		flat = -flat;
	}
	printf("%lf", sum);
	return 0;
}
